Liquid crystal display (LCD for short) device, due to its advantages of small size, low power consumption, less radiation, and the like, has become a mainstream product of flat-panel display devices at present. A backlight is an essential component of the liquid crystal display device and is used for providing back light for the display panel in display.
A side type backlight is usually adopted in order to facilitate a tendency of the display panel to be thinner and lighter. In the side type backlight, a light source is generally arranged at an edge of a light guide plate on one side thereof, so that the light emitted from the light source enters the light guide plate from a side surface of the light guide plate edge. The light source in the backlight is usually a LED light bar. A conventional LED light bar is generally assembled by a plurality of LEDs with the same brightness level, so as to ensure a good light-entering effect. However, in a backlight product, a plurality of LED light bars with several brightness levels are needed to satisfy the manufacture requirement. The brightness levels of the LEDs in different light bars may be different in a backlight product, which results in wide fluctuation range of brightness of the backlight product, which uses various light bars.
In order to solve the problem of wide fluctuation range of brightness of the backlight product which uses various light bars, the backlight in a current large-size display panel usually uses a LED light bar with mixed brightness as the light source. The LED light bar with mixed brightness refers to that the LEDs with different brightness (for example, different batches of LEDs) are alternately arranged on a flexible printed circuit (FPC) board and this arrangement can mix the brightness of LEDs with different brightness, so that the brightness of various LED light bars assembled by LEDs with different brightness tends to be uniform, thereby reducing the brightness fluctuation among various backlights.
FIG. 1 illustrates the arrangement of backlight in the above-mentioned large-size display panel. The LED light bar is assembled by a plurality of first LEDs 5 and second LEDs 6. The brightness of the plurality of first LEDs 5 is the same and the brightness of the plurality of second LEDs 6 is the same, the brightness of the first LEDs 5 is different from that of the second LEDs 6. The plurality of first LEDs 5 and the plurality of second LEDs 6 are arranged on a printed circuit board 4 alternately, so as to mix the brightness of the LEDs 5 with the brightness of the LEDs 6, and thereby the brightness of various backlights tends to be uniform.
Similarly, at present, in a small-size display panel, the problem of wide fluctuation range of brightness among various backlights is attempted to be solved by using the light source arranged as above. However, since the back light area in the small-size display panel is relatively small, the small-size display panel is sensitive to brightness mixing. A glowworm phenomenon (i.e., a plurality of alternately dark and bright dots appear on the display panel due to a great contrast between the high brightness area and the low brightness area) is likely to occur when brightness mixing of the light sources with different brightness is realized in a small area. As a result, the above arrangement of the light source for brightness mixing in the large-size display panel may not solve the problem of wide fluctuation range of brightness among various backlights in the small-size display panel.